Substituted thiobis phenolic compounds and antioxidant protection therewith



United States Patent 3,364,174 SUBSTITUTED THIOBIS PHENOLIC 'COMPGUNDS AND AN TIOXIDANT PROTECTION THEREWITH Ralph Arthur Coleman, Middlesex, Frank Meritt Fur-man,

Bridgewater Township, Somerset County, and Jerry 5 Peter Miiionis, Franklin Township, Somerset County, N.J., assignors to American Cyanamid Company, Stamford, Conn, a corporation of Maine No Drawing. Filed Apr. '1, 1964, Ser. No. 356,644

5 Claims. (Cl. 260-45.95)

ABSTRACT OF THE DISCLOSURE A polymeric olefin composition comprising an olefin polymer having dispersed therein in an antioxidant amount a substituted thiobis phenolic compound of the structure to impart to the substrate improved antioxidant protection.

This invention relates to new thiobis phenolic derivatives and, more particularly, to thiobis aromatic hydroxy compounds represented by the Formula I:

wherein A is a trimethylene or a tetramethylene radical. The hydroxy groups may be either on the 1- or the 2- position; and when the hydroxyl group is in the l-position, the S is attached to the 4-position.

The new compounds are useful as antioxidants in various types of polymeric systems, particularly polyolefins. They are effective at low concentrations, soluble in polyolefins and are heat stable. Thus, they can be milled into polyolefin formulations at high temperatures without losing effectiveness.

The compounds of this invention are conveniently prepared by the reaction of a 5,6,7,8-tetrahydro naphthol or an indanol with sulfur dichloride (SCl in an inert solvent such as benzene, hexane, methyl cyclohexane and diethyl ether. The reaction proceeds readily at room temperature, but warming to temperatures of C. or C. speeds the reaction. In some instances, a catalyst (such as aluminum chloride) may be used to give improve-d results.

The reaction between sulfur dichloride and the indanol or tetrahydronaphthol may give mixtures of isomeric products in which the thio bridge is attached in different positions. For example, when 5,6,7,8 tetrahydro-2-naphthol is reacted with sulfur dichloride, a mixture of isomers actually results, attack taking place in the 1- and 3-p0sitions, resulting in a mixture of the 1,1'-isomer, the 3,3- isomer and the 1,3'-isomer. From this mixture, the 3,3- thiobis naphthol and the corresponding 1,1'-isomer may easily be isolated in the pure state.

When 5,6,7,8-tetrahydro-l-naphthol is reacted with sulfur dichloride at room temperature, substantially only the 4,4-isomer is obtained.

In the reaction of the indanols with sulfur chloride, the sulfur attachment is in the 4-position when the phenolic group is in the l-position. When the phenolic group is in the 2-position, the sulfur attaches to the 3-position.

In all of the above preparations, completion of the reaction is evidenced by the precipitation of the product and also substantial decrease in the evolution of hydrogen chloride.

The compounds of this invention may be used alone or in isomeric mixtures as obtained above. They are especially useful in polyolefins such as polyethylene, polypropylene, polybutylenes and copolymers thereof. However, they are useful in polymeric materials such as polyvinyl chloride, polystyrene, acrylonitrile, butadiene-styrene copolymers, polyacrylates, nylon and other polyamides, etc.; and also in other organic compositions subject to deterioration by oxidative attack such as gasoline, lubricating oils, waxes, lard, rubber, etc.

For the purpose of rotection against oxidative deterioration, the compounds of this invention are incorporated into the substrate material in an amount of broadly about 0.001 to 5.0% and, specifically, about 0.05 to about 1.0%, based on the weight of the total stabilized composition.

The invention is further illustrated by the examples which follow. Parts and percentages are on a Weight basis unless otherwise specified.

EXAMPLE 1 3,3'-thi0bis(5,6,7,8-zetrahydr0-2-naphtlz0l) In a 250-ml. flask are charged: 74 g. (0.5 mole) 5,6,7,S-tetrahydro-Z-naphthol ml. ethylenedichloride and slowly 50 g. (0.37 mole) aluminum chloride then 31.8 ml. (0.5 mole) sulfur dichloride.

After stirring for 24 hours at room temperature, the mixture is drowned in one liter of water and 50 ml. of concentrated hydrochloric acid. The ethylene-dichloride is evaporated off on a steam bath and water is removed by decantation. Tar is extracted with two liters-of water containing 100 ml. of 20% caustic. The extract is acidilied and liquor is decanted from the tar that forms. After trituration with about 25 ml. of methanol, the solid is filtered off and hexane-washed. This material is purified by dissolving in 25 ml. of benzene and activated charcoal and reprecipitating with 25 ml. of hexane. A buffwhite product (M.P. 174176 C.) is obtained.

EXAMPLE 2 1,] '-th i0bis-5 ,6, 7,8-tez'rahydr0-Z-naphthol Into a 1-liter flask (stirrer, nitrogen blanket, ice bath) are charged:

162.8 g. (1.1 m.) 5,6,7,8-tetrahydro-2-naphthol 250.0 ml. ethyl ether When the solid dissolves, the solution is cooled to 5 C. and a solution of:

31.6 ml. (0.5 m.) sulfur dichloride 50.0 ml. ethyl ether is added in one hour at 5 C.

After stirring overnight at room temperature, almost all of the ether is evaporated under tap vacuum on a warm steam bath. Methylcyclohexane (250 ml.) is added. The mixture is cooled and permitted to stand. The product is filtered off and washed with hexane. The white solid (M.P. 178-184 C.) is recrystallized from 300 ml. .of CH OH, giving the product (M.P. 191-193 C.).

EXAMPLE 3 Thibis-5,6,7,8-tetrahydro-2-izaphthol (mixture of 1,1 isomer, 1,3-is0mer and 3,3-is0mer) In a 2-liter flask (stirrer, nitrogen blanket) are charged:

266 g. (1.8 mole) tetrahydro-Z-naphthol 450 ml. methylcyclohexane To this, at C. in minutes, there is added dropwise, a solution consisting of:

ml. methylcyclohexane 47.4 ml. (0.75 mole) sulfur dichloride After stirring overnight at 40 C., 300 ml. of hexane is added and the mixture is cooled to 10 C. The product is filtered off and washed with hexane. A gray white solid (M.P. 100-110 C.) is obtained after air-drying.

EXAMPLE 4,4'-thi0bis(5,6,7,8tetrahydro-I -naphthol) To a solution of 1.4 grams 5,6,7,8 tetrohydro-lnaphthol in 10 m1. benzene is added, dropwise, a solution of 1.0 gram sulfur dichloride in 5 ml. benzene. The product, 4,4-thiobis (5,6,7,8-tetrahydro-l-naphthol), is filtered, washed with petroleum ether and air-dried (M.P. 193-200 C.).

EXAMPLE 5 7,7-thiobis(4-indanol) HO S To'a solution of 2.2 grams 4-indanol in 30 ml. benzene, is added, dropwise, with stirring, a solution of 2.0 grams sulfur dichloride in 20 ml. benzene. The reaction mixture is stirred for fifteen minutes and filtered. The product is isolated as a grayish-white solid (M.P. l204 C.).

EXAMPLE 6 4 EXAMPLE 7 Comparative testing and use as antioxidant I. SAMPLE PREPARATION METHODS A. Solvent casting of polyethylene films.Polyethylene films were cast from xylene solution in the following manner. A solution of 10% polyethylene in xylene, containing 0.1% of antioxidant on the weight of resin, is cast on a glass plate heated to about C. A four-inch pulldown bar with a gate of approximately 100 mills is employed to cast the solution. The material is left at 100 C. for 20 minutes and then placed in an oven at C. for 20 minutes longer to evaporate off the last traces of xylene, after which time the plate is cooled and a film of about 3 to 5 mils thick is stripped olf. For the oxygen uptake experiment, each sample is composed of six thicknesses of films, /6 inch x 2 /2 inches; whereas, the carbonyl formation test is performed on a single thickness of film, with the dimensions 1% inches x inch, supported on sodium chloride crystal plates.

B. Milling and molding of polyethylene and olypropylena-Tests were made also on films prepared by milling and compression-molding. The milling was done on a two-roll laboratory mill. The general procedure of milling and molding the three resins is as follows: After 100 grams of resin are fluxed onto the hotter roll (about one minute), the antioxidant is added, and the material given 40 passes (about four minutes) through the mill. From the milled sheet, roughly inch thick, a sample of about 2 inches x 2 inches is cut and molded into a film. The milling and the molding conditions employed for the various resins are tabulated.

Milling Molding Temperature Resin Total 7 Film Temp. Force Time Thick- Front Back F.) (Tons) (Min) ness Roll Roll (Mils) Polyethylene. 350 350 Polypropylene" 350 375 350 The dimensions of the specimens taken for testing were the same as those for the solvent-cast polyethylene films, except that single thicknesses of film were used in both tests. A

II. TEST METHODS Two methods of testing were employed to determine antioxidant efiiciency: (1) rate of oxygen uptake, where the film samples are subjected to pure oxygen at one atmosphere and 140 C.; and (2) rate of,.carbonyl formation at 140 C. in an air-circulating oven. The result for both tests is reported as an induction period (defined as the number of hours of protection afforded to the resin III. TEST RESULTS Tables I and ILcontain the results of oxygen uptake and carbonyl formation experiments in low density polyethylene.

Values for 1,l-thiobis(2-naphthol) are included for comparison purposes. 7

Table III contains polypropylene evaluation test data.

TABLE I.SOLVENT-OAST POLYETHYLENE FILM Oxygen Uptake Carbonyl Formation Antioxidant Percent Hrs. to Induction Cone. Absorb Induction Period 10 cc. 03 Period (Hours) per g. (Hours) Resin Control (no additive) 3. 3 3. 4 3. 0 3,3-thiobis (5,6,7,8-tetrahydro-2- naphthol) 0.1 432, 331 439, 340 8.1 l,l-thiobis(2-naphthol) 0. 1 110 125 32. 3

TABLE H MOLDED POLYETHYLENE FILM sistant to deterioretive action of oxygen by incorporeting [Antioxidant at 01% com] therem in an antioxidant amount, a substituted thiobls phenol compound of the structure Oxygen Uptake FCarbotnyi 011E3- 10D. Antioxidant Induction Absorb I d P d 10 Ge. 02 n no 1011 one 1 A perg eenod) (Hours) A S N Resin ours l Control (no additive) 2.5 2.0 3.3 3,3"thiobis(5,6,7,8-tet1ahydr0- wherein A is selected from the group consisting of tngxgg fi gg- 322") 318'0 methylene and tetramethylene chains.

Tnioi i s gs tgm-tetrah dro- 335 340 0 143 5 155 3. The polyolefin composition of claim 2 wherein the 2-na o 225 235 H55 substituted thiobis phenol compound has the followlng 7,7-thiobis(4-indanol) 98 100 120; 104 structure 1,l-thiobis(2-naphthol) 56. 5 54. 5 33. 5

OH HO TABLE IIIPOLYPROPYLENE (SAMPLE PREPARATION) 5 METHOD B 1 Percent 835;: fig 4. The polyolefin composition of claim 2, wherein the Antioxidant Conc. 140 0. Induction substituted th10b1s phenol compound has the followin Induction Period t t I. a

Period (Hours) 5 P110 11 6 (Hours) Control (no additive) 0.5 2.2 3,3-thiobis(5,6,7,8-tetrahydro-2 2-naphtho1) 0.2 34.0 25.8 ii iii t i ii t b d 101s erayroii i i tik'isi'rr'n H OH 10 1s e ra oit-Hammer -3 0.2 49 T p lyolefin COIIIPOSIUOII of claim 2, Wheleln the substituted th1ob1s phenol compound has the following structure We claim:

1. A composition consisting essentially of a polyolefin S and from 0.001% to 5.0% by weight, of a compound 50 represented by the formula: 0

OH H

OH OH S References Cited A A UNITED STATES PATENTS 3,252,911 5/1966 OIlOff 26045.95 X

wherein A is selected from the group consisting of tri- OTHER REFERENCES methylene and tetramethylene chains. Mousseron, P IeHd- 1942, PP-

2. An olefin polymer selected from the group consist- I ing of polyethylene, polypropylene, and ethylene-propyl- DONALD CZAJA Pnmary Exammerene copolymers which polymers have been rendered re- M. J. WELSH, Assistant Examiner. 

